The invention relates to an electrical connector used in a well head equipment for transmitting electrical signals between the inside and the outside of the well head. Such a connector is particularly important in oil wells which are fitted with permanent sensors, e.g. temperature or pressure sensors, since it serves to feed the sensors with electrical power and to transmit the signals from the sensors to a remote point at the surface.
For the purposes of the present description, the term "well head equipment" is used to designate all of the equipment situated between the production tubing of a well and the flow line coming out of the valve assembly or "Christmas tree". This term thus covers both well head equipments which are disposed in the air and equipments which are underwater, e.g. offshore.
Well head equipments are essentially constituted by two parts: the well head and the valve assembly (or Christmas tree).
In conventional manner, electrical connections are provided through well head equipments by means of connectors comprising pins and sockets which mate with one another when the valve assembly is installed on the well head. The sockets are mounted inside the valve assembly and they are connected to the outside of the valve assembly via a sealed electrical feedthrough. The pins are mounted on the hanger from which the production tubing is suspended and they are connected to the annular space lying between the casing and the tubing via a second sealed feedthrough.
However, such a connector suffers from several drawbacks. Firstly, since it is at a distance from the axis of the well head, it is necessary for the valve assembly to be in exact angular alignment and for both axial and radial positioning tolerances to be exact when the valve assembly is put into place on the well head. In addition, insulation losses may occur in the presence of a conducting fluid such as sea water if it invades the space enclosing the connector. Finally, the connector contact is not protected from galvanic corrosion phenomena.
More recently, an article which was published in the July 1988 edition of the journal "World Oil", at pages 43-44 and entitled "Electrically Controlled Subsea Safety Valve" describes an inductively coupled electrical connection for transmitting electrical power through a subsea well head for the purpose of powering a safety valve situated in the tubing. To this end, inductive coupling is provided by means of two concentric coils both of which are placed beneath the hanger from which the tubing is suspended. An outer coil is wound around the well head, and an inner coil is wound around the tubing.
However, this inductive-coupling connection for a subsea well head also suffers from drawbacks. In this connection the outer coil is an integral portion of the fixed parts of the well head, and any repair work on the outer coil requires major disassembly of the items constituting the well head.
The object of the invention is to provide an inductive-coupling connector which avoids the above-mentioned drawbacks, which is reliable, which withstands attack from the medium in which it is immersed, and which is easy to maintain.